PUCCINIA POARUM 



47 



as shown in radial section. The outer edge of each cell is more 

 prolonged downwards so as to overlap a portion of the cell 

 below in an imbricated manner. The aecidium, in both, as is the 



Fig. 27. P. Poarum. An recidio- 

 spore germinating on leaf of 

 Poa annua. x 180. 



Fig. 26. P. Poarum. Vertical section 

 through edge of aecidium ; showing a, 

 the crushed cells of the upper myce- 

 lium, pushed on one side ; b, the chain 

 of peridium-cells ; c, the spore bed, 

 giving rise to d, the chains of a?cidio- 

 spores. x 600. The black dots are 

 the nucleoli ; one aecidiospore-inother- 

 cell has three nuclei. 



case in most of the higher forms 



of the Uredinales, arises deep Fig. 28. p. Poarum. o.ansecidio- 



spore germinating in water, 

 m the leaf, and the densely x 250 ; b, the same, showing 

 packed knot of hyphse which the germ-pores, x500. 



forms the starting-point of the hymenium, where the cells are 

 full of protoplasm, is covered over by a number of nearly empty 

 cells which are ultimately squeezed to the side by the develop- 

 ing aecidium and are shown in the figure at a. 



It is easy to produce the teleutospores in a garden on a tuft 

 of (say) Poa annua or P. pratensis, by planting quite near to it 



